This invention relates to a multiplex communication system and more particularly to a system which is capable of transmitting a plurality of signal channels over a common transmission line and then deriving each of said channels without the use of a separate synchronization means.
The concept of multiplexing has been widely employed in the communications field and essentially consists of combining two or more signals into a single multiplex signal which signal can be transmitted on a single channel. At the receiving end, the multiplex signal is processed to recover the individual signals.
In any event, many prior art systems utilize relatively complicated circuits to assure that the multiplex transmitter is synchronized with the multiplex receiver. As such, the prior art systems are relatively complicated and difficult to implement. Generally speaking, in most prior art systems, there is a necessity to provide a synchronizing signal which signal is retrieved by a separate circuit at the receiving end and is then employed to assure that the individual signals are properly recovered in the correct time sequence. Such techniques have been referred to as framing circuits and so on.
Essentially, there is a need to provide a simplified multiplexing system to enable the transmission of a plurality of signals over a single transmission channel. While the technique to be described has many applications, there is a particular application which exists in aircraft or similar types of public transportation. For example, in a modern airliner each passenger location such as a passenger seat may receive a plurality of audio channels, each of which can be selected by the passenger to enable him to listen to any one of a wide variety of musical programs. As is ascertained, the wiring in the aircraft may be extremely complicated in order to direct each of the channels to the passenger location. If a multiplex system is employed, then there may be problems with synchronization and so on.
It is therefore an objective of the present invention to provide a simplified and efficient system which is capable of multiplexing a plurality of channels on a common transmission channel and then responding to the multiplexed wave to regenerate each of the channels at a receiving end. The system to be described employs a unique synchronization technique which is inherently part of the multiplex signal and which enables the receiver to regenerate a series of reference signals indicative of each of the multiplex channels.